Dublin blamed after mortar attacks: RUC warned MI5 of mainland 'spectacular' but terrorists' trail ran cold in Republic

John Major called three key Cabinet ministers to Downing Street talks yesterday to tackle intelligence lapses and step up the campaign against IRA terrorism in Britain in the wake of the three recent Heathrow mortar attacks.

The Prime Minister was also warned that the RUC is highly critical of the security services in the Irish Republic, which it says have not co-operated fully enough against terrorists. Ministers believe the RUC may be seeking to shift the blame from its own failures but Mr Major is seeking an urgent meeting with Albert Reynolds, the Irish Prime Minister, to improve cross-border security.

The Independent has learnt that some weeks before the Heathrow attacks the RUC warned MI5, which co- ordinates measures against terrorism, that the IRA was planning a 'spectacular' in Britain. Police at the Commons were also put on alert after the RUC tipped off the security services that noted IRA terrorists had left 'their usual haunts', according to a source. The RUC asked Irish counterparts to track the terrorists when they crossed into the Republic, but the trail ran cold.

Security sources believe the mortars were assembled in the Republic and smuggled to Britain. An Armagh group known for expertise in explosives is high on the list of suspects.

James Molyneaux, the Ulster Unionist leader, expressed RUC concern about the security failures and lack of co-operation on intelligence operations from the South when he met the Prime Minister yesterday. Their meeting was cut short after 50 minutes to enable Mr Major to discuss the Government's response to the IRA's new campaign with Malcolm Rifkind, Secretary of State for Defence; Michael Howard, Home Secretary; and Sir Patrick Mayhew, Secretary of State for Northern Ireland.

Defence sources confirmed the Army wants greater freedom for helicopters to overfly the border area. One source said: 'The Defence Secretary is also angry that there is still no direct contact between the two armies, North and South, and we still have to go through the Garda (Irish police).' The Republic is reluctant to allow this because it wants the police to remain in the lead on terrorism.

A senior Irish government source last night played down any suggestion of intelligence shortcomings and pointed to significant arms finds in recent weeks, including big hauls in Donegal and Westmeath.

Claims of a lack of Irish co-operation are seen in Dublin as an attempt at a political excuse. Calls for British helicopters to be allowed to overfly the border have been made before.

A small bomb was discovered by a railway worker on the London-bound track near Sevenoaks station in Kent yesterday.

It could have been planted as long ago as December, when the station and others were closed after a coded warning of a bomb on the Sevenoaks- London line. There were no warnings yesterday.

In Belfast, the RUC warned that the IRA was using a highly sensitive remote control unit for mortar and other attacks which could be triggered accidentally. The Californian-made control unit, on sale in Northern Ireland and Britain, is used in the photographic industry and activated by infra-red transmitters.

However, flashing car headlights in the rain, warning lights on ambulances and fire engines, and even the infra-red beam from a car's central locking device could activate the unit.

The RUC believes that the IRA has been using the device to set off bombs and mortars from up to 800ft (250 metres) away.